Cellulose derivative composition



Q? R Patented May UNITED STATES PATENT OFFICE CELLULOSE DERIVATIVECOMPOSITION SEARCH ROOM y S arold James Tattersall, Ardrossan, Scotland,FOR MISSING assignor to Imperial Chemical Industries Limited, acorporation of Great Britain No Drawing. Application July 25, 1938,Serial No. 221,239. In Great Britain August 10, i 2 193s .5

14 Claims. (Cl. 106-40) 7 Reference is made to my application Serial No.156,603 filed July 30, 1937, entitled Nitrocellulose compositions ofreduced infiammability which claims the use of the salts described belowin nitrocellulose compositions.

The present invention relates to the production of improved cellulosederivative compositions and more particularly to the production of suchcompositions having reduced infiammability.

This invention has as an object the preparation of cellulose derivativecompositions of reduced inflammability. A further object is theproduction of cellulose g eriya gve films of good transparency aftdr'educed inflammagility. A still further object is the production ofcellulose derivative films of reduced infiammability which has anincreased tolerance for filling ingredients. Further objects will appearhereinafter. These objects are accomplished by the following invention.i

I have found that the presence of a metallic or non-metallic salt ofdimethyl phosphoric acidi'if'a c'e'llulose 'derivativeb(impositionreduces the infiammability characteristics of the films, coatings,filaments or other products obtained from the cellulose composition.

The present invention consists, therefore, in cellulose derivativecompositions such as, cellulose ethers or esters, for example celluloseacetate compositions, in which for the purpose of reducing theinflammability and optionally for the purpose'df i mproving the otherproperties of the composition as hereinafter described, there isincluded a salt of dimethyl phosphoric acid.

Certain organic salts of dimethyl phosphoric acid, when incorporatedwith cellulose ethers and carboxylic acid esters, permit of theformation of films or other products which are substantiallytransparent; and these salts also possess a plasticising actionresulting in the production or films of improved flexibility. Asexamples of such salts, there may be mentioned the dimethyl phosphatesof ammonium, cadmium and cerium and also of hydrazine, phenylurea,diphenylurea, urethane, diphenyl-guanidine, triethanolamine and methylallophanate, etc. Such salts are preferably those derived from organicbases of low molecular weight. It is generally preferred, moreover, toemploy salts derived from organic bases which contain within themolecule an ester group or other active solvent group. The trans-,parent flexible iire-resistant g o np o sitions prepared with the al arthe described salts of able in the productioii of Celluloid-likematerials, for example in the manufacture of cinema or photographicfilm. The compositions of my invention are of importance in photographicfilm which has a light sensitive layer upon at least one side thereof.

Certain other salts of dimethyl phosphoric acid,

' when incorporated with cellulose ethers and carboxylic acid esters,form films or other products having varying degrees of translucency oropacity. Suitable proportions of these salts may be added withoutcausing embrittlement of the films formed from the compositions inquestion and some of them at least also possess a plasticising action onthe films. As examples of salts there may be mentioned certainnon-metallic salts, e. g. the salts of urea and guanidine, and certainmetallic salts, e. g. those of calcium, bari- 1 um, magnesium, lead,aluminum, zinc, copper, co-

balt, manganese, antimony and thallium. The films obtained fromcellulose ether and carboxylic acid ester compositions containing suchmetallic or non-metallic salts may be rendered less opaque or even insome cases transparent by the incorporation of a plasticizer with thecellulose ether and carboxylic acid ester or other similar non-volatilematerial. In the manufacture of transparent or translucent films, it ispreferred to avoid the inclusion of any substantial proportion ofinflammable material of a plasticising nature, e. g. camphor or dibutylphthalate, and for this reason, therefore, it is preferred to use thosesalts which yield directly a product of the desired degree oftransparency and flexibility.

In manufacturing relatively opaque compositions, it may, however, bedesirable to employ such salts of dimethyl phosphoric acid which possessa plasticising action in order to increase the tolerance of thecomposition for filling ingredients, pigments and the like. I have alsofound that I can obtain desirable results by incorporating such salts ofdimethyl phosphoric acid with cellulose ethers and esters byincorporating the salts with the cellulose derivative in a plasticisedcondition and evaporating off any volatile constituents.

The salts of dimethyl phosphoric acid in general confer no undersirableodour to the plastic compositions and this property presents a distinctadvantage, since many of the flame-retarding ingredients which havehitherto been proposed have been organic compounds characterised by anobjectionable odour or other objectionable properties which can beavoided by choosing a suitable salt of di n ethyl phosphoric acid. Otherproposals have involved the usecf inorganic fire-retarding agents butthey, on the whole, yielded disappointing results since the large amountof such material required has usually resulted in embrittlement of theplastic.

I have further found that the inflaznmability of compositions containingcellulose derivatives and a salt of dimethyl phosphoric acid may befurther reduced by the incorporation of a relatively small proportion ofa number of inorganic compounds, several of which have no injuriouseflect upon the clarity of the film obtained. These accessory compoundsare stable colourless salts soluble in organic solvents and free fromoxidising action. Among these compounds there may be mentioned ammoniumhypophosphite, calcium tartrate, mercuric potassium iodide, sodiumfluoride, stannic chloride, titanium sulphate, uranyl acetate and bariumhypophosphite. It is particularly desirable to incorporate a smallproportion of these compounds along with the simple urethane salts ofdimethyl phosphoric acid since a good reduction in infiammabilityoccurs.

The invention is further illustrated but is not intended to be limitedby the following examples in which the parts given are parts by weight.

Example 1 100 parts of cellulose acetate are dissolved in acetone andincorporated with 25 parts of the urethane salt of dimethyl phosphoricacid. The solution is then made into transparent flexible films by anormal casting process. When a flame is brought into contact with such afilm charring takes place in immediate contact with the flame; butceases immediately when the flame is withdrawn, without any trace ofsmouldering.

Example 2 100 parts of benzyl cellulose are dissolved in a mixture oftoluol volumes) and industrial alcohol (20 volumes), and incorporatedwith from 10 to 25 parts of the urethane salt of dimethylphosphoricacid. The solution is made into a flexible film by a normal castingprocess, and produces a transparent or translucent material which isuninflammable and does not smoulder after being inserted in a flame andremoved therefrom.

Example 3 100 parts of ethyl cellulose are incorporated with 25 parts ofurethane dimethyl-phosphoric acid in the manner described in Example 1.The plasticised ethyl cellulose shows greatly reduced infiammability incomparison with the untreated material when cast into films in the usualmanner.

Other cellulose derivatives which can be .treated in this way arecellulose propionate, cellulose butyrate, cellulose oleate, cellulosenitroacetate, cellulose aceto-butyrate, ethyl-benzyl cellulose, methylcellulose.

Any proportion of dimethyl phosphates will have some fire-proofingaction but this is seldom of practical value until their proportionreaches 10 per cent on the weight of cellulose derivative. The upperlimit to the proportion of salts varies with the salt used. When usingurethane dimethyl phosphate a proportion higher than 25 per centproduces a film which is too soft. Salts which have less plasticisingaction than the urethane salt could be present in higher proportions.

If the dimethyl phosphates are ground. for instance, in a colloid mill,before addition to the cellulose derivative composition solution ahigher degree of translucency can be obtained in the final film. Thegrinding process can be continued till the finest state of division isobtained and I get greater translucency the more finely the salts areground.

This invention is a valuable advance in the art since it makes itpossible to reduce the inflammability of plasticised cellulosederivative compositions without the disadvantages of objectionable odouror colour, While the retarding ingredients do not embrittle the plasticand in some cases even act as a plasticiser, and also those salts ofdimethyl phosphoric acid that exert a plasticising action on thecellulose derivative also confer a high tolerance for inert fillers,even in a plastic containing a considerable proportion of cellulosederivative. Compositions made up with cellulose acetate and urethanedimethyl phosphate with the addition of plasticisers are useful as cablelacquers, in which use it is particularly important that they should benon-inflammable.

As many apparently widely different embodi ments of this invention maybe made without departing from the spirit and scope thereof, it is to beunderstood that the invention is not limited to the specific embodimentsthereof except as defined in the appended claims.

I claim:

1. A cellulose derivative composition taken from the class consisting ofcellulose ethers and carboxylic acid esters having incorporated thereina salt of dimethyl phosphoric acid.

2. A cellulose derivative composition taken from the class consisting ofcellulose ethers and carboxylic acid esters having incorporated thereina salt of dimethyl phosphoric acid, which possess plasticisingproperties.

3. A cellulose derivative composition taken from the class consisting ofcellulose ethers and carboxylic acid esters having incorporated thereinan organic salt of dimethyl phosphoric acid.

4. A cellulose derivative composition taken from the class consisting ofcellulose ethers and carboxylic acid esters having incorporated thereinan organic salt of dimethyl phosphoric acid of low molecular Weight.

5. A cellulose derivative composition taken from the class consisting ofcellulose ethers and carboxylic acid esters having incorporated thereinan organic salt of dimethyl phosphoric acid of low molecular weight andpossessing plasticizing properties.

6. A cellulose derivative composition taken from the class consisting ofcellulose ethers and carboxylic acid esters having incorporated thereinan organic salt of dimethyl phosphoric acid of low molecular weightcontaining an active solvent group.

7. A cellulose derivative composition taken from the class consisting ofcellulose ethers and carboxylic acid esters having incorporated thereina salt of dimethyl phosphoric acid, and a suitable colorless saltsoluble in organic solvents and free from oxidizing action.

8. A cellulose acetate composition containing a salt of dimethylphosphoric acid.

9. A benzyl cellulose composition containing a salt of dimethylphosphoric acid.

10. An ethyl cellulose composition containing a salt of dimethylphosphoric acid.

11. A composition as set forth in claim 1 wherein the salt is theurethane salt.

12. A composition as set forth in claim 1 wherein the salt is thecalcium salt.

13. A composition as set forth in claim 1 wherein the salt is the leadsalt.

14. A cellulose acetate composition containing the urethane salt ofdimethyl phosphoric acid.

HAROLD J. TAT'I'ERSALL.

